[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 050836
TCDAT1
TROPICAL STORM IDA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112009
400 AM EST THU NOV 05 2009

THE SATELLITE PRESENTATION OF IDA HAS CONTINUED TO IMPROVE OVER THE
PAST FEW HOURS. EARLIER THERE WAS A LARGE EXPANSION OF COLD CLOUD
TOPS IN A SYMMETRIC CENTRAL DENSE OVERCAST WHILE IN THE LAST HOUR OR
TWO THE COLDEST TOPS HAVE TAKEN ON A MORE BANDED APPEARANCE. DVORAK
INTENSITY ESTIMATES AT 0600 UTC WERE 55 KT FROM TAFB AND SAB...
HOWEVER AIRCRAFT RECONNAISSANCE FOUND THAT IDA WAS ALREADY THAT
STRONG YESTERDAY WHEN IT HAD A MUCH LESS IMPRESSIVE SATELLITE
APPEARANCE.  THEREFORE...THE INITIAL INTENSITY IS RAISED TO 60 KT
FOR THIS ADVISORY.  WHILE THERE IS ONLY A SMALL WINDOW FOR
ADDITIONAL STRENGTHENING...THE HURRICANE WATCH FOR PORTIONS OF THE
COAST OF NICARAGUA REFLECTS THE SMALL CHANCE THAT IDA COULD REACH
HURRICANE STATUS AS IS MAKES LANDFALL.  AFTER LANDFALL...WEAKENING
IS FORECAST AS THE CENTER IS EXPECTED TO REMAIN OVER LAND FOR THE
NEXT COUPLE OF DAYS.  THE TRACK FORECAST TAKES IDA BACK OVER THE
NORTHWESTERN CARIBBEAN SEA AFTER 48 HOURS...AND THE INTENSITY
FORECAST SHOWS SOME STRENGTHENING AT 72 HOURS AND BEYOND.  HOWEVER
...THERE IS A LARGE DEGREE OF UNCERTAINTY AT THIS TIME RANGE...SINCE
IDA MAY NOT SURVIVE LONG ENOUGH TO REACH WATER AGAIN.

THE INITIAL MOTION ESTIMATE IS 310/06. THROUGH 48 HOURS THE
MULTI-MODEL CONSENSUS IS IN GOOD AGREEMENT WITH THE PREVIOUS
FORECAST...AS IDA IS EXPECTED TO TURN NORTHWARD BETWEEN A WEAK
MID-LEVEL RIDGE OVER THE NORTH-CENTRAL CARIBBEAN SEA AND A
WEAK TROUGH OVER THE SOUTHERN GULF OF MEXICO.  BEYOND THAT TIME...
MUCH OF THE GUIDANCE HAS SHIFTED WESTWARD WITH LARGE DIFFERENCES IN
FORWARD SPEED AS WHATEVER IS LEFT OF IDA INTERACTS WITH A MID-LEVEL
TROUGH DIGGING INTO THE NORTHWESTERN GULF OF MEXICO.  GIVEN THE
LARGE SPREAD IN THE GUIDANCE...A SLOW NORTH-NORTHWESTWARD MOTION IS
SHOWN AT DAYS 3 THROUGH 5.  THIS IS IN GOOD AGREEMENT WITH THE
PREVIOUS FORECAST AND ON THE EASTERN SIDE OF THE GUIDANCE
ENVELOPE...WITH THE EXCEPTION OF THE GFDL WHICH IS A FAR EASTERN
OUTLIER.

THE BIGGEST IMPACT OF THIS SLOW-MOVING SYSTEM WILL LIKELY BE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES CAUSED BY EXTREMELY
HEAVY RAIN OVER PORTIONS OF NICARAGUA AND HONDURAS OVER THE NEXT
COUPLE OF DAYS.

FORECAST POSITIONS AND MAX WINDS

INITIAL      05/0900Z 12.8N  83.4W    60 KT
 12HR VT     05/1800Z 13.3N  83.9W    45 KT...INLAND
 24HR VT     06/0600Z 13.9N  84.3W    35 KT...INLAND
 36HR VT     06/1800Z 14.7N  84.6W    30 KT...INLAND
 48HR VT     07/0600Z 15.7N  84.8W    25 KT...INLAND
 72HR VT     08/0600Z 18.0N  85.5W    35 KT...OVER WATER
 96HR VT     09/0600Z 20.0N  86.0W    40 KT
120HR VT     10/0600Z 22.0N  87.0W    45 KT

$$
FORECASTER BRENNAN/CANGIALOSI

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